In this context, Cameron's inability to emerge from the shadow of UKIP is irresponsible. Even the most hardened Eurosceptic should see that the fragmentation of democracy in Europe, coupled with Russia's recent belligerence, changes Britain's strategic interests. The only greater folly than the creation of the eurozone would be its uncontrolled disintegration. Even if the major parties recoil from discussing it in detail, recent polling suggests that foreign policy does matter to the UK electorate: 63 per cent of the public say that the UK should aspire to be a "great power", even if a decade of strategic drift in Iraq and Afghanistan has left them wary of foreign intervention. If the rise of populist politics is fundamentally about the value gap between the people and political elites, this surely represents an important point of congruence upon which the mainstream parties have failed to capitalise.

The most important lesson from Syriza's victory is that it demonstrates the political value of a strong narrative and vision. Both Cameron and Miliband have failed to articulate a grand strategy, a coherent sense of what Britain stands for, its place in the world and the ability to align actual interests and capabilities. These are difficult questions, particularly in a period of economic austerity but the debate has barely changed in the quarter-century since the end of the Cold War. It is hardly surprising that populist politics has filled this vacuum, conflating domestic concerns about British sovereignty within Europe with genuine debate about challenges to British and international security.

The effect has been a hollowing-out of British foreign policy and a consequent diminution of our security. The starkest illustration is Cameron and Miliband's quixotic approach to military intervention. Cameron came to power describing himself as a "liberal Conservative". This oxymoron was hard to decipher at the time and unsurprisingly it translated into confused foreign policy. In opposition, Cameron spoke dismissively of Tony Blair's attempts to "drop democracy out of an aeroplane at 40,000 feet." In power, however, Cameron has been hamstrung by his attempts not to make the same mistakes as Blair. This has resulted in strategic illogicality and a worsening of policy outcomes.

Cameron embraced multilateral intervention in Libya in 2011 whilst also pushing for Security Council authorisation. In this he was supported by Miliband. Downing Street suggested that this was a template for future interventions—the apparently successful multilateral support for local democratic emergence, supported with airstrikes and without risking the lives of British soldiers. This model was trumpeted as a success, long after its consequences became disastrously apparent, and it has continued to shape subsequent interventions. It has revealed a desire to act on the world stage that has not been matched with any thought for the consequences or the will to maintain Britain's capabilities. Cameron's international engagement is based on a disappearing world in which the UK acts in partnership with an America that is actively engaged in maintaining international stability and is prepared to act as military backstop to Nato. None of these suppositions are as stable as they were even a decade ago, yet parliamentary debate suggests that they inform the foreign policy thinking of both main parties.